[PATCH v1 6/8] xen/riscv: introduce early_printk basic stuff

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

The patch introduces a basic stuff of early_printk functionality
which will be enough to print 'hello from C environment"

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
 xen/arch/riscv/Kconfig.debug              |  7 ++++++
 xen/arch/riscv/Makefile                   |  1 +
 xen/arch/riscv/early_printk.c             | 27 +++++++++++++++++++++++
 xen/arch/riscv/include/asm/early_printk.h | 12 ++++++++++
 4 files changed, 47 insertions(+)
 create mode 100644 xen/arch/riscv/early_printk.c
 create mode 100644 xen/arch/riscv/include/asm/early_printk.h

diff --git a/xen/arch/riscv/Kconfig.debug b/xen/arch/riscv/Kconfig.debug
index e69de29bb2..940630fd62 100644
--- a/xen/arch/riscv/Kconfig.debug
+++ b/xen/arch/riscv/Kconfig.debug
@@ -0,0 +1,7 @@
+config EARLY_PRINTK
+    bool "Enable early printk config"
+    default DEBUG
+    depends on RISCV_64
+    help
+
+      Enables early printk debug messages
diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 60db415654..e8630fe68d 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -1,6 +1,7 @@
 obj-$(CONFIG_RISCV_64) += riscv64/
 obj-y += setup.o
 obj-y += sbi.o
+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
 
 $(TARGET): $(TARGET)-syms
 	$(OBJCOPY) -O binary -S $< $@
diff --git a/xen/arch/riscv/early_printk.c b/xen/arch/riscv/early_printk.c
new file mode 100644
index 0000000000..f357f3220b
--- /dev/null
+++ b/xen/arch/riscv/early_printk.c
@@ -0,0 +1,27 @@
+/*
+ * RISC-V early printk using SBI
+ *
+ * Copyright (C) 2021 Bobby Eshleman <bobbyeshleman@gmail.com>
+ */
+#include <asm/sbi.h>
+#include <asm/early_printk.h>
+
+void early_puts(const char *s, size_t nr)
+{
+    while ( nr-- > 0 )
+    {
+        if (*s == '\n')
+            sbi_console_putchar('\r');
+        sbi_console_putchar(*s);
+        s++;
+    }
+}
+
+void early_printk(const char *str)
+{
+    while (*str)
+    {
+        early_puts(str, 1);
+        str++;
+    }
+}
diff --git a/xen/arch/riscv/include/asm/early_printk.h b/xen/arch/riscv/include/asm/early_printk.h
new file mode 100644
index 0000000000..05106e160d
--- /dev/null
+++ b/xen/arch/riscv/include/asm/early_printk.h
@@ -0,0 +1,12 @@
+#ifndef __EARLY_PRINTK_H__
+#define __EARLY_PRINTK_H__
+
+#include <xen/early_printk.h>
+
+#ifdef CONFIG_EARLY_PRINTK
+void early_printk(const char *str);
+#else
+static inline void early_printk(const char *s) {};
+#endif
+
+#endif /* __EARLY_PRINTK_H__ */
-- 
2.38.1